The present invention is related to a metal belt used as a power transmission means in a belt type infinite variable-speed drive and in particular to a metal belt that comprises metal element members.
This type of metal belt is known from the past and has been disclosed in, for example, Japanese Laid-open utility model publication No. 62-131143(A) and Japanese Laid-open patent publication No. 2-225840(A). These metal V-belts are comprised by an endless belt shaped metal ring member and a plurality of metal element members supported along the metal ring member transmitting power between a drive pulley and a driven pulley. Both of these pulleys can variably control the V-channel width and by means of variably controlling the V-channel width of both pulleys, the wrapping radius of the V-belt on both pulleys can be changed and in addition the change gear ratio can be changed in infinite steps.
As described in, for example, the ASME: International Computers in Engineering Conference and Exhibition vol. 3 (1987) pp461-465, concerning the behavior of the metal element member s (hereinafter referred to as elements) during the operation of this type of metal V-belt, two regions are known to exist especially at the arcing portion directed away from the driven pulley towards the drive pulley. In one of these regions (close to the driven pulley outlet) a gap occurs between the front and rear element members and in the other region (close to the drive pulley inlet) no gap occurs between the front and rear elements and they are joined together.
The method stated in Japanese Laid-open patent publication No. 7-12177(A) is known concerning friction and improvements to the efficiency in this type of metal V-belt. In a metal V-belt, the geometric relationship between the pulleys and the belt causes the belt to travel imprecisely between the pulleys with the elements invading into the drive pulley in a state in which the elements are leaning somewhat within a plane at a right angle to the metal ring member (hereinafter referred to as ring). If this state is allowed to exist, friction of the V-surface and reductions in the power transmission efficiency will occur due to one side making contact with the pulley V-surface.
Thereupon, when the contact position between the innermost peripheral surface of the ring and an element and the distance in the horizontal direction between two contact positions of the outermost peripheral surface of the ring and an element is A and the clearance between the outermost peripheral surface of the ring and an element is B, the position of the contact point of the ring and the element is specified such that angle tanxe2x88x921 B/A becomes smaller than 1 degree. By means of specifying the position is this manner, the ring restricts the oscillation angle of the element at the drive pulley inlet which in turn improves the friction and power transmission efficiency.
However, a definite method to set the angle tanxe2x88x921 B/A to 1 degree or less is not disclosed in the above-mentioned applications. Furthermore, as stated in the above-mentioned applications and literature, in this type of metal V-belt it is necessary to ensure a sufficientdegree of freedom for the translation movement of the elements and for the forward and rearward leaning in order to restrict the thus termed closure movement that occurs in the outlet arcing portion of the driven pulley against the elements. This lead to a serious problem of appropriately setting the values A and B of the above equation.
Also, the front and rear elements mutually interact through both coupling portions in the unstable region of the driven pulley outlet arcing portion and in the pulley inlet portion when the pulley width changes. At this time the coupling portions are allowed to oscillate as a shaft center. This oscillation is restricted by contact between the ring and the element portion. At the contact portion at this moment, surface pressure acts on the ring and the element in proportion to the rotation moment of the element.
The magnitude of this surface pressure was greatly affected by the lifespan of the metal ring member that is comprised by a plurality of especially thin metal rings approximately 0.2 mm thick stacked on eachother and reducing this surface pressure was a major issue for improvements in the lifespan of the ring.
The object of the present invention is to restrict the oscillation angle without obstructing the forward and rearward leaning or the translation movement of the elements as well as stabilizing the state of the elements close to the pulley inlet.
Another object of the present invention is to reduce oscillation and noise by means of stabilizing the state of the elements, control the V-surface friction of the pulleys and improve the power transmission efficiency.
A further object of the present invention is to improve the durability of the ring that comprises the metal belt.
In the present invention the metal belt that transmits power between the drive pulley and the driven pulley is comprised by a metal ring member consisting of a plurality of endless belt shaped metal ring members stacked on each other (for example, ring 20 in the embodiment) and a plurality of metal element members supported along the ring (for example, element 10 in the embodiment). If the distance between where the outermost peripheral surface of the ring and the element make contact with the above-mentioned shaft center is Lxcex1 and if the distance between where the innermost peripheral surface of the ring and the element make contact with the above-mentioned shaft center is Lxcex2, the metal belt MV will be comprised to have the relationship (Lxcex1/Lxcex2) greater than 0.8 when the shaft that goes through the center of the coupling disposed on the front and rear surfaces of the element as well as passes through the principal plane of the element in the direction through the front and rear surfaces functions as a shaft center and the element is allowed to oscillate.
In other words, the elements of the metal belt of the present invention are comprised such that the oscillation angle is made smaller than conventional elements by means of shifting the contact point between the outermost peripheral surface of the ring (for example, 20a in the embodiment) when the elements oscillate and the surface facing the bottom of the elements (for example, the lower surface of the ear portion 12a in the embodiment) relative to the outermost peripheral surface of the ring toward outside of the pulleys.
Alternatively, the elements are comprised such that xcex1 less than xcex2 when the ring is located at the center position of the element slot when the oscillation angle that causes the outermost peripheral surface of the ring and the surface facing the bottom of the elements relative to this surface is xcex1 and the oscillation angle that causes the innermost peripheral surface of the ring and the surface facing the top of the elements is xcex2 at the moment when the elements oscillate centered on the center shaft of the couplings in like manner to the above composition.
According to these types of compositions, it is possible to reduce the entire oscillation angle of the elements without narrowing the clearance between the elements and the ring (for example, total clearance CL in the embodiment). Namely. reductions in the oscillation angle can be achieved without restricting the translation movement of the elements and forward leaning angle (without sacrificing the closure movement of the elements).
Further, according to the above-mentioned compositions, the contact position when the elements oscillate and the outermost peripheral surface of the ring and the lower surface of the ear portion make contact shifts from the coupling center (shaft center) by an amount that equals the increase in the length of the arm of the moment. And when an oscillation movement having the same amount of movement occurs, the surface pressure acting on the ear portion and the outermost peripheral surface of the ring can be reduced.
Furthermore, the metal belt of the present invention is comprised such that the diameter of the approximate cylindrical shaped concave portion (for example, hole 15 in the embodiment) is larger than the diameter of the approximate cylindrical shaped convex portion (for example, nose 14 in the embodiment) at the front and rear couplings (namely, has a gutter when joined).
The above-mentioned composition makes it possible to increase the clearance between the couplings of the front and rear elements while maintaining the element oscillation angle identical to a conventional case. Consequently, this makes it possible to increase the allowable width with respect to the coupling center shifting between the front and rear elements at the driven pulley outlet portion.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.